Threaded Tee-nut fastening devices are widely used in the furniture industry for securing components of furniture together. Such Tee-nuts are formed of sheet metal, and incorporate on internally threaded sleeve or barrel, and an integral face flange, and spikes, which are embedded in the work piece around a pre-drilled hole. They are used, for example, in the construction of beds, for securing legs to a bed frame, and other furniture items.
Various forms of apparatus have been devised for the power-operated setting of such Tee-nuts at a high rate of speed. One example of such a Tee-nut setting apparatus is shown in U.S. Pat. No. 3,460,217.
The apparatus disclosed in that patent has operated satisfactorily for many years. In that apparatus, the wooden workpiece was first of all placed on a lower working surface. Tee-nuts were fed from a hopper down a curved, gravity slide, to a power-operated setting plunger located above the work piece. The Tee-nut was held in registration with the bottom of the plunger, and when the plunger was operated downwardly the Tee-nut was released, and the plunger struck the Tee-nut forcing it downwardly into a hole in the workpiece.
One problem in the design of such earlier machines was that they required the use of a hopper, and a relatively expensive feed mechanism, for feeding the loose Tee-nuts. These requirements added to the complexity and hence the expense of such earlier apparatus. These factors had, in turn, limited the scope of the sales of such machines. In practice, they were economical only for relatively large scale manufacturing facilities.
Another problem was that the Tee-nuts did not always slide smoothly in the slide. Occasionally the operator had to release jammed Tee-nuts.
A further proposal is shown in U.S. Pat. No. 4,821,940, granted to Allan C. Rotherham entitled Tee-nut Insertion Machine.
In this machine, a hopper and feed mechanism generally similar to that shown in earlier Tee-nut insertion machines, was used. However, in this machine, the Tee-nuts were fed to a feed mechanism from which they were delivered one at a time to a plunger. The plunger in this case operated with an upward insertion stroke, so that the Tee-nut was forced upwardly into the workpiece. Above the workpiece, a stationary anvil or support was located against which the workpiece was held, while the Tee-nut was forced upwardly. In this device, however, the Tee-nuts were simply placed loose in the hopper as in the earlier devices, and as a result, it was necessary to provide for a two position delivery system for delivering the Tee-nuts to the plunger.
The Tee-nuts were delivered to a preliminary insertion location, at which point they stopped. The end most Tee-nut was then moved over a ledge, one at a time by a piston, from the preliminary location, to the so called extended location, in which position it was then held ready for insertion by the plunger.